We don't have synonyms for arthritides yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are arthritis, arthritide and arthritics.
(n) :
Inflammation of a joint or joints causing pain and/or disability, swelling and stiffness, and due to various causes such as infection, trauma, degenerative changes or metabolic disorders: any of several disease entities.
(n) :
Inflammation of a joint or joints causing pain and/or disability, swelling and stiffness, and due to various causes such as infection, trauma, degenerative changes or metabolic disorders: any of several disease entities.